Electrochromic properties of bis(phthalocyaninato)lutetium(III) sensitized nanostructured anatase TiO₂ thin films

Nanoporous TiO₂ anatase thin films have been sensitized with bis(phthalocyaninato)lutetium(III) complexes (Pc₂Lu) and their electrochromic properties were investigated at room temperature in neutral and acidic aqueous media. Cyclic voltammetry and spectroelectrochemistry measurements show that the typical neutral green color state of Pc₂Lu is reduced to a brown color state at potentials below -0.3 V vs. Ag/AgCl at neutral pH when Pc₂Lu is adsorbed onto a nanostructured TiO₂ surface. Disproportionation of the complex while scanning in aqueous medium is assumed to be responsible for this behavior.